Seasonal and Diurnal Variation in Atmospheric Ammonia in an Urban Environment Measured Using a Quantum Cascade Laser Absorption Spectrometer

Abstract

Extensive measurements were made using an Aerodyne quantum cascade laser absorption spectrometer (QCLAS) to study the diurnal and seasonal cycles of NH 3 concentrations in Manchester city centre. Measurements made at rooftop levels showed traffic to be a significant source of NH 3 concentrations in the winter. This was illustrated by a bimodal diurnal cycle of NH 3 concentrations that was synchronized with traffic, and also by a correlation with NO x , a traffic related pollutant. These patterns were not observed during the summer, suggesting other sources become more important. Measurements were also made at street level during winter and summer, close to the traffic source. This time the contribution from traffic was also observed in the summer, albeit weaker. Enhanced NH 3 concentrations were often seen in winds from the southwest that could not be related to local sources, suggesting that ambient concentrations in the city are strongly influenced by sources outside the city. It is estimated that the total NH 3 emission from the city centre is between 0.7 and 2.3 t km −2 year −1 .

Open-path, quantum cascade-laser-based sensor for high-resolution atmospheric ammonia measurements

“…More recently, advances in room temperature, distributedfeedback quantum cascade (QC) lasers have led to the development of QC-laser-based NH 3 sensors using the strongest NH 3 absorption transitions located in the mid-infrared spectral region (Manne et al, 2006;Whitehead et al, 2007;McManus et al, 2008;Manne et al, 2009;Curl et al, 2010;Ellis et al, 2010;Gong et al, 2011). Although these closedpath systems are highly sensitive (ppbv or sub-ppbv), they suffer from sampling artifacts that limit precision and response time and complicate calibration methods (Whitehead et al, 2008;von Bobrutzki et al, 2010).…”

Variation of Urban Atmospheric Ammonia Pollution and its Relation with PM2.5 Chemical Property in Winter of Beijing, China

“…In some cities around the world, measurements of ambient NH 3 have been reported, for example, in Rome (Perrino et al, 2002), New York City (Li et al, 2006), Manchester (Whitehead et al, 2007), Barcelona (Pandolfi et al, 2012) and Seoul (Phan et al, 2013). In China, continuous measurements of NH 3 spanned over a year have been reported in Beijing (Meng et al, 2011) and Xi'an (Cao et al, 2009), which focused on characterizing the levels and variations of NH 3 .…”

Characterizing a Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) for measurements of atmospheric ammonia

“…Chemiluminescence-based instruments offer higher time resolution, but this indirect method is prone to interferences and false positives (Winer et al, 1974;Dunlea et al, 2007;Steinbacher et al, 2007). More recent techniques involve the use of spectroscopic instruments and chemical ionization mass spectrometry (CIMS), which provide high time resolution and are both specific and sensitive to NH 3 , but are often expensive and challenging to deploy in field conditions (Li et al, 2006;Nowak et al, 2007;Whitehead et al, 2007). A summary of instrument figures of merit for different NH 3 measurement techniques can be found in von Bobrutzki et al (2010).…”